Semiconductor device

ABSTRACT

To improve noise immunity of a semiconductor device. A wiring substrate of a semiconductor device includes a first wiring layer where a wire is formed to which signals are sent, and a second wiring layer that is mounted adjacent to the upper layer or the lower layer of the first wiring layer. The second wiring layer includes a conductor plane where an aperture section is formed at a position overlapped with a portion of the wire  23  in the thickness direction, and a conductor pattern that is mounted within the aperture section of the conductor plane. The conductor pattern includes a main pattern section (mesh pattern section) that is isolated from the conductor plane, and plural coupling sections that couple the main pattern section and the conductor plane.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 14/590,291, filed on Jan. 6, 2015, which claims priority from thedisclosure of Japanese Patent Application No. 2014-012155 filed on Jan.27, 2014 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present invention relates to technology for a semiconductor device,and relates to technology effective for example in semiconductor devicescontaining a semiconductor chip mounted over a wiring substrate havingplural stacked wiring layers.

2. Related Art

Signal transmission paths to electrically couple circuits formed overthe semiconductor chip and external devices are formed over the wiringsubstrate where the semiconductor chip is mounted. To render theimpedance discontinuities formed over these signal circuit pathsharmless a discontinuity cancellation technology is employed thatcancels the impedance discontinuity by utilizing an inverse impedancediscontinuity.

A technology is disclosed for example in Japanese Unexamined PatentApplication Publication No. 2004-253947 (patent document 1) in which athird planar circuit having a characteristic impedance higher than afirst planar circuit; and a fourth planar circuit having acharacteristic impedance higher than a second planar circuit areserially coupled between a first planar circuit, and a second planarcircuit having a higher characteristic impedance than the first planarcircuit.

Also, the non-patent document 1 for example discloses a technology formatching an average impedance to a 50 ohm impedance by enclosing thefront and back of a low-impedance section configured from a through viaand a solder ball pad by a high-impedance line.

The non-patent document 2 for example discloses technology for matchingan average impedance in a signal transmission path including alow-impedance section configured from a through via and a solder ballpad to a 50 ohm impedance by way of a conductor layer formed in ainductor configuration by combining a small via and a wiring pattern.

[Non-Patent Document 1]

-   Nanju Na, Mark Bailey and Asad Kalantarian, “Package Performance    Improvement with Counter-Discontinuity and its Effective Bandwidth”,    Proceedings of 16th Topical meeting on Electrical Performance of    Electronic Packaging, p. 163 to p. 166 (2007)    [Non-Patent Document 2]-   Namhoon Kim, Hongsik Ahn, Chris Wyland, Ray Anderson, Paul Wu,    “Spiral Via Structure in a BGA Package to Mitigate Discontinuities    in Multi-Gigabit SERDES System”, Proceedings of 60th Electronic    Components and Technology Conference, p. 1474 to p. 1478 (2010)

SUMMARY

However, when employing the method for applying an inverse impedancediscontinuity section in the opposite direction along the transmissionpath in order to cancel out the impedance discontinuity section, thefrequency of the signal becomes higher and in some cases where theimpedance cannot be cancelled out this state might function as a doubleimpedance discontinuity. In other words, along the signal transmissionpath of the high-frequency signal, a signal is reflected at the boundaryof the impedance discontinuity that is approximately twice the impedancediscontinuity. Consequently, a countermeasure is required so that theimpedance discontinuity section approaches the specified impedance (forexample 50 ohms).

When an aperture section is formed over the conductor pattern of aseparate layer to cover the section where the impedance discontinuityoccurs in order to cancel out the capacitive impedance discontinuity,inductive crosstalk noise is prone to easily occur in that section sincethe return path (reflux current path) corresponding to the signaltransmission path and the signal transmission path are separate fromeach at localized points.

Other novel features and issue will become readily apparent from theaccompanying drawings and the description in the present specifications.

According to an aspect of the present invention, a wiring substrate in asemiconductor device includes a first wiring layer where a first wire towhich signal are sent is formed, and a second wiring layer that ismounted adjacent to the upper layer or the lower layer of the firstwiring layer. Also, a first conductor plate where a first aperturesection is formed at a position overlapped with a portion of the firstwire in the thickness direction; and a first conductor pattern placedwithin the first aperture section of the first conductor plate areformed over a second wiring layer. The first conductor pattern containsa mesh pattern section isolated from the first conductor plate; andplural coupling sections linking the mesh pattern section and theaforementioned conductor plate.

According to the aspect of the present invention, noise immunity of thesemiconductor device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the semiconductor device of the presentembodiment;

FIG. 2 is a bottom view of the semiconductor device shown in FIG. 1;

FIG. 3 is a perspective plan view showing the internal structure of thesemiconductor device over the wiring substrate in a state with the heatsink removed;

FIG. 4 is a cross-sectional view taken along the lines A-A of FIG. 1;

FIG. 5 is an enlarged cross-sectional view showing an example of thewiring structure of the stripline;

FIG. 6 is an enlarged cross-sectional view showing an example of thewiring structure of the microstrip line;

FIG. 7 is an enlarged plan view showing an example of the planar shapeof the conductor pattern serving as the electromagnetic wave absorber;

FIG. 8 is an enlarged cross-sectional view taken along the wireextension direction shown by the dotted lines in FIG. 7;

FIG. 9 is an enlarged cross-sectional view for a position different fromFIG. 8;

FIG. 10 is an enlarged perspective view showing the essential structureof the conductor pattern for the enlarged view in FIG. 9;

FIG. 11 is an enlarged cross-sectional view showing a modificationcorresponding to FIG. 9:

FIG. 12 is an enlarged plan view showing a modification corresponding toFIG. 7;

FIG. 13 is an enlarged plan view showing another modificationcorresponding to FIG. 7;

FIG. 14 is an enlarged perspective view showing the periphery of theconductor pattern of FIG. 13;

FIG. 15 is a drawing for describing the flow in the assembly process forthe semiconductor device shown in FIG. 1 through FIG. 4;

FIG. 16 is a drawing for diagrammatically describing the productionprocess for forming the conductor pattern serving as the electromagneticwave absorber over the wiring substrate in the substrate preparationprocess of FIG. 15;

FIG. 17 is an enlarged plan view showing a modification examplecorresponding to FIG. 7;

FIG. 18 is an enlarged plan view showing another modification examplecorresponding to FIG. 7;

FIG. 19 is an enlarged plan view showing another modification examplecorresponding to FIG. 7;

FIG. 20 is an enlarged plan view showing another modification examplecorresponding to FIG. 7.

DETAILED DESCRIPTION Description of Format, Basic Terminology, and Usagein these Specifications

In the present specifications, the description of the embodiment isdivided into plural sections for purposes of convenience as needed,however unless specifically stated otherwise these are not mutuallyseparate units and regardless of the overall description are singleexamples of a section, one section being a detailed sectional part ofanother section, or is one part or is the entire modification, etc. Alsoas a general rule, repetitive descriptions of the same sections areomitted. Also unless specifically stated to the contrary, among thestructural elements in the embodiments, the structural element is notrequired except when logically limited to a stated quantity and exceptwhen clearly stated in the context.

Also, in descriptions about materials and compositions such as “Xcomprised of A”, except for the case where specifically stated otherwiseor the case where clearly stated otherwise from the context in thedescription of the embodiments, the description is not exclusive ofelements other than A. Among ingredients for example, the descriptionmay signify “X comprising A as the main ingredient”, etc. Even amongexpressions such as “silicon member”, the members are not simply limitedto silicon, and may of course be SiGe (silicon and germanium) alloy orother multi-element alloys utilizing Si as the main ingredient, ormembers including other additive elements. Also, among gold plating,copper (Cu) layers, and nickel and plating and so on, unless statedotherwise or unless specifically stated, the member is not a simpleelement and may also include gold, copper (CU), nickel, or otherelements as the main ingredient.

Moreover, even in the case of a designated numerical value or numericalquantity, except when logically limited to a stated quantity or exceptwhen clearly stated otherwise in the context, the numerical value mayexceed that designated numerical value and also be a numerical valuebelow that designated numerical value.

The terms planar surface and side surface are utilized in thesespecifications. The semiconductor element forming surface of thesemiconductor chip serves as the reference surface, and the levelsurface parallel to that reference surface is described as the planarsurface. Moreover, the surface intersecting the planar surface isdescribed as the side surface. The direction joining the two planarsurfaces that are positioned apart from one another as seen from theside surface is described as the thickness direction.

The terms upper surface or lower surface are also utilized in thepresent specifications. However, there are various semiconductor packagemounting states so after mounting the semiconductor package the uppersurface might for example be placed below the lower surface in somecases. In the present specifications, the planar surface of thesemiconductor element forming surface side of the semiconductor chip, orthe planar surface of the chip mounting surface side of the wiringsubstrate, is described as the upper surface; and the surface that isplace on the side opposite the upper surface is described as the lowersurface.

In each of the drawings in the embodiment, identical sections or similarsections are shown by identical or similar numbers or reference numbers,and the description is generally not repeated.

In the accompanying drawings, hatching may be omitted even on crosssections if the drawings are complicated or if gaps can be clearlyidentified. In this connection, if clarified by the description, thecontour lines in the background might be omitted even for level closedholes. Moreover, hatching or a dot pattern may be added in order toclearly specify there is no gap or to clearly indicate the boundary of aregion even if not a cross section.

Embodiment

FIG. 1 is a perspective view of the semiconductor device of the presentembodiment. FIG. 2 is a bottom view of the semiconductor device shown inFIG. 1. FIG. 3 is a perspective plan view showing the internal structureof the semiconductor device over the wiring substrate in a state withthe heat sink removed. FIG. 4 is a cross-sectional view taken along thelines A-A of FIG. 1. In FIG. 1 through FIG. 4, the number of terminalsis reduced to improve the visual understanding. In FIG. 4, the number ofsolder balls 4 is reduced more than in the example shown in FIG. 2 forbetter visual understanding. Though omitted from the drawings, thenumber of terminals (bonding pad 2PD, land 2LD, solder ball 4) can matcha variety of modifications other than the states shown in FIG. 1 throughFIG. 4.

<Semiconductor Device>

The overall structure of the semiconductor device 1 of the presentembodiment is first of all described while referring to FIG. 1 throughFIG. 4. The semiconductor device 1 of the present embodiment includes awiring substrate 2, and a semiconductor chip 3 (see FIG. 4) mounted overthe wiring substrate 2.

The wiring substrate 2 as shown in FIG. 4 is comprised of an uppersurface (surface, main surface, first surface, chip mounting surface) 2a over which the semiconductor chip 3 is mounted, a lower surface(surface, main surface, second surface, mounting surface) 2 b on theside opposite the upper surface 2 a, and the plural side surfaces 2 s(see FIG. 1 through FIG. 3) placed between the upper surface 2 a andlower surface 2 b, and that a formed in the external shape of a squareas seen from a plan view as shown in FIG. 2 and FIG. 3.

The wiring substrate 2 is an interposer (relay substrate) forelectrically coupling the semiconductor chip 3 mounted over the uppersubstrate 2 a side and the mounting substrate not shown in the drawing;and is comprised of plural wiring layers (six layers in the exampleshown in FIG. 4) that electrically couples the lower surface 2 b sideserving as the mounting surface and the upper surface 2 a side servingas the chip mounting surface. The wiring substrate 2 is for exampleformed by stacking in layers by the build-up technique for each of theplural wiring layers, over the upper surface 2Ca and lower surface 2Cbof the insulation layer (core layer, core material, core insulationlayer) 2CR comprised of prepreg material in which resin is permeatedinto glass fibers. The wiring layer for the upper surface 2Ca side, andthe wiring layer on the lower surface 2Cb side of the insulation layer2CR, are electrically coupled by way of plural through hole wiring 2TWembedded in the plural through holes formed so as to penetrate fromeither one side to the other side of the upper surface 2Ca and lowersurface 2Cb.

FIG. 4 shows a wiring substrate 2 containing an insulation layer 2CRwhich is a core layer as one example of a wiring substrate however amodification relative to FIG. 4 contains no core or in other wordsutilizes a so-called coreless substrate. In this case, no through holewire 2TW is formed, and the wiring layer for the lower layer 2 b sideand the wiring layer for the upper layer 2 a side are electricallycoupled by way of plural via wires 2V for contact with each wiringlayer.

Plural bonding pads (terminals, semiconductor chip coupling terminals)2PD are formed over the upper surface 2 a of the wiring substrate 2 forelectrical coupling to the semiconductor chip 3. Plural lands(terminals, external terminals, external electrodes) 2LD serving asexternal input/output terminals for the semiconductor device 1 areformed over the lower surface 2 b of the wiring substrate 2. The pluralbonding pads 2PD and plural lands 2LD are each electrically coupled byway of the plural via wires 2V serving as the interlayer conduction pathand the plural wires 2 d formed in the wiring substrate 2. In theexample shown in FIG. 4, an insulation layer 2CR serving as the corelayer is contained over the wiring substrate 2. Therefore, the uppersurface 2Ca side and the lower surface 2Cb side of the insulation layer2CR are coupled by way of the through hole wire 2TW that conductors (forexample, a metal such as copper) are embedded in a through hole formedso as to pass through from one side to the other of either the uppersurface 2Ca and the lower surface 2Cb of the insulation layer 2CR. Thestructure of each wiring layer of the wiring substrate 2 is described indetail later on.

In the example in FIG. 4, solder balls (solder material, terminals,external terminals, electrodes, external electrodes) 4 are coupled tothe respective plural lands 2LD. The solder balls 4 are a conductivematerial for electrically coupling the plural terminals on the mountingboard side (omitted from drawing) to the plural lands 2LD, duringmounting the semiconductor device 1 over a mounting board not shown inthe drawing. The solder balls 4 are for example a solder material thatis an Sn—Pb solder material containing lead (Pb) or not essentiallycontaining lead or namely a solder material made from lead-free solder.Examples of lead-free solder are for example, tin (Sn) only, tin-bismuth(Sn—Bi), or tin-copper-silver (Sn—Cu—Ag), lead-copper (Sn—Cu), etc.Here, the term lead-free solder signifies a lead (Pb) content of 0.1percent weight by volume and this content was established as a standardin the RoHS (Restriction on Hazardous Substances) directive.

The plural solder balls 4 as shown in FIG. 2 are placed in a matrixshape (array shape, matrix shape). Though omitted from the drawing inFIG. 2, the plural lands 2LD (see FIG. 4) where the plural solder balls4 are joined are also positioned in a matrix shape. A semiconductordevice where plural external terminals (solder ball 4, land 2LD) areplaced in a matrix shape on the mounting surface side of the wiringsubstrate 2 is called an area array type semiconductor device. Areaarray type semiconductor devices are capable of effectively utilizingthe mounting surface side (lower surface 2 b) of the wiring substrate 2as a space for placing the external terminal and so are preferable inthe point that having to increase the mounting surface area of thesemiconductor device can be prevented even if the number of externalterminals is increased. In other words, semiconductor devices using anincreasing number of external terminals according to high functionalityand high integration can be mounted in space-saving.

In the examples shown in FIG. 1, FIG. 2, and FIG. 4 so-called BGA (BallGrid Array) type semiconductor packages utilizing the solder balls 4 asexternal terminals were shown as examples, however there are a varietyof modifications in the structure and the layout of the externalterminals. For example in the lower surface 2 b shown in FIG. 4,modifications may include a structure where plural lands 2LD are exposedor a structure joining thin solder material over plural lands 2LD thatare exposed in the lower surface 2 b. Semiconductor packages havingthese type of modifications are called LGA (Land Grid Array).

The semiconductor device 1 includes a semiconductor chip 3 mounted overthe wiring substrate 2. As shown in FIG. 4, each of the semiconductorchips 3 contains a surface (main surface, upper surface) 3 a, a rearsurface (main surface, lower surface) 3 b on the opposite side of thesurface 3 a, and a side surface 3 s that is positioned between thesurface 3 a and the rear surface 3 b. The semiconductor chip 3 as shownin FIG. 3 forms a square outer shape whose surface area is smaller thanthat of the wiring substrate 2 as seen from a plan view. In the exampleshown in FIG. 3, each of the four side surfaces 3 s of the semiconductorchip 3 are mounted in the center section of the upper surface 2 of thewiring substrate 2 so as to extend along the respective four sidesurfaces 2 s of the wiring substrate 2.

Plural pads (bonding pads) 3PD are formed over the surface 3 a of thesemiconductor chip 3 as shown in FIG. 4. In the present embodiment,plural pads 3PD are placed in a matrix shape (matrix shape, array shape)over the surface 3 a of the semiconductor chip 3. Positioning the pluralpads 3PD serving as electrodes for the semiconductor chip 3 in a matrixshape is preferable since the surface 3 a of the semiconductor chip 3can be efficiently utilized as a space for positioning the electrodes,so that having to increase the surface area can be prevented even ifthere is an increase in the number of electrodes for the semiconductorchip 3. Though not shown in the drawing, a modification of the presentembodiment is capable of being applied to semiconductor chip types whereplural pads are formed over the periphery of the surface 3 a.

In the example shown in FIG. 4, the semiconductor chip 3 is mounted overthe wiring substrate 2 in a state where the surface 3 a is facingopposite the upper surface 2 a of the wiring substrate 2. This type ofmounting method is called the face down method or the flip chip method.

Though not shown in the drawings, plural semiconductor elements (circuitelements) are formed over the main surface (more specifically, asemiconductor element forming region formed over the element formingsurface of the semiconductor substrate serving as the base material ofthe semiconductor chip 3) of the semiconductor chip 3. The plural pads3PD are respectively electrically coupled to the plural semiconductorelements by way of the wiring (omitted from the drawing) formed over thewiring layer placed internally (more specifically, between thesemiconductor element forming region not shown in the drawing and thesurface 3 a) in the semiconductor chip 3.

The semiconductor chip 3 (more specifically, base material of thesemiconductor chip 3) is for example comprised of silicon (Si). Also, aninsulating film is formed over the surface 3 a so as to cover the wiringand the based material of the semiconductor chip 3. The respectivesurfaces of the plural pads 3PD are exposed from the insulating film byan aperture formed in that insulating film. The plural pads 3PD arerespectively comprised of metal and in the present embodiment arecomprised for example from aluminum (Al).

As shown in FIG. 4, the plural pads 3PD of the semiconductor chip 3 towhich the projecting electrodes 3BP are respectively coupled, and theplural pads 3PD of the semiconductor chip 3 are respectivelyelectrically coupled by way of the plural projecting electrodes 3BP tothe plural bonding pads 2PD of the wiring substrate 2. The projectingelectrodes 3BP are a metal member formed so as to protrude over thesurface 3 a of the semiconductor chip 3. The projecting electrode 3BP inthe present embodiment is a so-called solder bump where solder materialis stacked over the pad 3PD by way of an under-layer metal film(under-bump metal). This under-layer metal film can for example beexemplified as a laminated film in which for example titanium (Ti),copper (Cu), nickel (Ni) (in some cases a film of gold (Au) if furtherformed over a film of nickel) are stacked in layers from the sidecoupled to the pads 3PD. The solder material comprising the solder bumpmay for example utilize solder material containing lead or utilizinglead-free solder the same as for the above described solder ball 4. Whenmounting the semiconductor chip 3 over the wiring substrate 2, a solderbump may be formed beforehand over both the plural pads 3PD and theplural bonding pads 2PD, and heat treatment (reflow soldering) performedin a state where the solder bumps are in contact with each other formsthe projecting electrodes 3BP by integrating the solder bumps. In onemodification of the present embodiment, a pillar bump comprised of asolder film on the leading edge of the conducting column comprised fromcopper (Cu) and nickel (Ni) may be utilized as the projecting electrode3BP.

Also as shown in FIG. 4, an underfill resin (insulating resin) 5 isdeposited between the wiring substrate 2 and the semiconductor chip 3.The underfill resin 5 is deposited so as to block the space between thesubstrate 3 a of the semiconductor chip 3 and the upper surface 2 a ofthe wiring substrate 2. The underfill resin 5 is comprised of insulating(non-conductive) material (such as resin material) and is deposited soas to seal the electrical coupling section (joint of the pluralprojecting electrodes 3BP) of the wiring substrate 2 and thesemiconductor chip 3. By depositing the underfill resin 5 in this way soas to seal the coupling section of the plural projecting electrodes 3BP,the strain occurring in the electrical coupling section of thesemiconductor chip 3 and the wiring substrate 2 can be alleviated.

<Wiring Structure of Signal Transmission Path>

The wiring structure of the signal transmission path among the wiringsubstrates 2 that are shown in FIG. 1 through FIG. 4 are described next.FIG. 5 is an enlarged cross-sectional view showing an example of thewiring structure of the stripline. FIG. 6 is an enlarged cross-sectionalview showing an example of the wiring structure of the microstrip line.FIG. 7 is an enlarged plan view showing an example of the planar shapeof the conductor pattern serving as the electromagnetic wave absorber.FIG. 8 is an enlarged cross-sectional view taken along the wireextension direction shown by the dotted lines in FIG. 7.

In FIG. 7, even though a plan view, hatching is applied to the conductorplane 2PL, and a dot pattern is applied to the main pattern section MPmof the conductor pattern MP1 in order to easily distinguish eachstructural section of the electromagnetic wave absorber from theconductor plane 2PL on the periphery of the electromagnetic waveabsorber. Also in FIG. 7, in order to clearly show the planar positionalrelation of the electromagnetic wave absorber and the wire 2 d formed inanother wiring layer separate from the electromagnetic wave absorber, anexample of the layout of the wiring 2 d configuring the signaltransmission path is shown by a dotted line. Moreover, the solder ball 4shown in FIG. 4 is omitted in FIG. 8 to make the drawing easier to viewand understand.

The plural transmission paths in the wiring substrate 2 of the presentembodiment include for example transmission paths (high-speedtransmission paths) for transmission of signals at transmission speedsfor example of approximately 10 Gbps (Gigabit per second) to 25 Gbps. Toachieve a high transmission speed along this type of signal transmissionpath, the widening of the electrical fields and the widening of theelectromagnetic fields to the periphery of the signal transmission pathis preferably suppressed in view of the need for better noise immunityalong the signal transmission path. Restated in other words, suppressingthe scattering of electromagnetic waves that are generated in the signaltransmission path can improve the noise immunity of signal transmissionpath.

A wiring structure to suppress the widening of electrical fields ormagnetic fields to the periphery of the signal transmission path is atechnology as shown in FIG. 5 and FIG. 6 that forms a conductor plane(conductor plate) 2PL serving as the metallic film that is formed in aplate shape so as to overlap the wire 2 d serving as the signaltransmission path in the thickness direction and that supplies astandard electrical potential such as a ground potential to theconductor plane 2PL.

In the example of a wiring structure shown in FIG. 5, a conductor plane2PL serving as the metal film in a plate shape is respectively formed inthe upper wiring layer for the wire 2 d, and the lower wiring layer forthe wire 2 d. Restated in other words, as seen from a side view, thewire 2 d is enclosed between the conductor plane 2PL formed in the upperwiring layer, and the conductor plane formed in the lower wiring layer.Moreover, a conductor plane 2PL is formed in the wiring layer of thesame layer as the wire 2 d so as to be isolated from the wire 2 d andthe area around the wire 2 d is enclosed by the conductor plane 2PL. Thewiring structure shown in FIG. 5 is called a stripline.

In the example of a wiring structure shown in FIG. 6 on the other hand,a conductor plane 2PL is placed in a lower layer of a wiring layer forthe wire 2 d. Also, a conductor plane 2PL is formed in the wiring layerof the same layer as the wire 2 d so as to be isolated from the wire 2 dand the periphery of the wire 2 d is enclosed by the conductor plane2PL. However, in the wiring structure shown in FIG. 6, the wire 2 d isformed in the uppermost layer of the wiring layer, so that the conductorplane 2PL is not formed over the upper layer of the wire 2 d. The wiringstructure shown in FIG. 6 is called a microstrip line.

In the case of the microstrip line shown in FIG. 6, the conductor plane2PL is formed below the wire 2 d at a position overlapped with the wire2 d in the thickness direction. An electrical field and anelectromagnetic field are therefore not prone to easily widen below thewire 2 d. Also, the conductor plane 2PL is formed so as to be isolatedfrom the wire 2 d in the wiring layer of the same layer as the wire 2 d,and the periphery of the wire 2 d is enclosed by the conductor plane2PL. An electrical field and an electromagnetic field are therefore notlikely to widen in the periphery of the wire 2 d as seen from a planview. However, there is no conductor plane 2PL formed upwards of thewire 2 d so an electrical field and an electromagnetic field istherefore more likely to widen upwards of the wire 2 d compared todownwards of the wire 2 d. Therefore there is greater susceptibility toeffects of dispersion of electromagnetic waves or effects from noisepropagation from other wires mounted in that vicinity compared to themicrostrip line shown in FIG. 5.

Therefore, on paths for propagating signals at high speed, the wirestructure for the strip line shown in FIG. 5 is superior to the wirestructure for the microstrip line shown in FIG. 6.

However in the wiring substrate 2 as shown in FIG. 4, the plural stackedwiring layers are electrically coupled, and the upper surface 2 a sideand lower surface 2 b side are electrically coupled. Applying astripline structure for all sections of the transmission path istherefore difficult and the transmission path also includes sectionwhere the wiring structure is subject to fluctuations. An example of asection subject to fluctuations in the wiring structure is the sectionfor the via wire 2V electrically coupled between the adjacent wiringlayers. The section coupling the land 2LD and the wire 2 d that is aportion of the signal transmission path and the section coupling thethrough hole land 2TL and the wire 2 d are particularly prone togenerate large signal reflections in the coupling section for the viawire 2V. Electromagnetic wave scattering (or dispersal) caused by thesignal reflections therefore easily tends to occur.

Another example of a fluctuation in the wiring structure can be found insections for example where the structure is changed from a stripline toa microstrip line or in section where the structure is changed from amicrostrip line to a stripline.

Here, scattering of electromagnetic waves progressing along thetransmission path tends to easily occur in sections where the wiringstructure is changed. When a portion of these scattered electromagneticreturn in the direction from which they originally came (or in otherwords, when a signal reflection occurs), the section where there is achange in the wiring structure along the transmission path is observedas a section of the impedance discontinuity. Therefore technology torender the section with the impedance discontinuity ineffective isrequired in order to improve the reliability of the semiconductor devicecontaining signal transmission paths for transmitting electrical signalsat high speed.

As described above, there is a method that adds an inverse impedancediscontinuity in the opposite direction in order to cancel out thesection with the impedance discontinuity. However, when utilizing thismethod, the impedance cannot be canceled out when the frequency of thesignal becomes high and in some cases renders the effect of twoimpedance discontinuities.

In order to cancel out capacitive impedance discontinuities anothermethod forms an aperture section over the conductor pattern (conductorplane 2PL) of another layer covering the section where the impedancediscontinuity occurs to suppress capacitive coupling. However in thecase of this method, the distance between the signal transmission pathand the return path (reflux current path) corresponding to the signaltransmission path is isolated at localized sections so that the targetsection is easily susceptible to inductive crosstalk noise.

Whereupon, the present inventors made a study of technology forhigh-speed transmission paths that effectively renders impedancediscontinuities ineffective. The present inventors consequently tooknotice of the fact that impedance discontinuities and signal reflectionshave the following relationship. Namely, rather than signal reflectionsoccurring because there are impedance discontinuities, the presentinventors found that a portion of the scattered electromagnetic wavesare observed as impedance discontinuities due to returning in thedirection that they originally came. In view of this fact, the presentinventors took note of the fact that if the scattered electromagneticwaves could be eliminated, then the impedance discontinuities can berendered ineffective regardless of the sign (capacitive, inductive) ofthe impedance discontinuity.

In the present embodiment, an electromagnetic wave absorber capable ofeliminating the scattered electromagnetic waves by converting thescattered electromagnetic waves into heat energy is mounted in thesection where the impedance discontinuity is observed or in other words,at a position overlapped with the section where the wiring structurechanges in the thickness direction along the signal transmission path.The electromagnetic wave absorber is comprised of a conductor of metal,etc.

In the examples shown in FIG. 7 and FIG. 8, the conductor pattern(metallic pattern) MP1 serving as the electromagnetic wave absorber isformed within the aperture section PLh formed over the conductor plane2PL as seen from a plan view. The conductor plane 2PL is for example aground plane (conductor plate for supplying a standard electricpotential) that supplies the standard electric potential (GND); and theaperture section PLh shown in FIG. 8 is formed so as to penetratethrough in the thickness direction of the conductor plane 2PL. Also, theconductor pattern MP1 is comprised of the main pattern section (meshpattern section) MPm isolated from the conductor plane 2PL, and theplural coupling sections MPj joining the main pattern section m and thecoupling sections MPj. The main pattern section MPm and the couplingsections MPj are respectively formed from the metal material (forexample utilizing copper as the main element) same as the conductorplane 2PL.

When signals are sent (signal current flows) in the wire 2 d which ispart of the signal transmission path, the electromagnetic waves scattertowards the periphery of the wire 2 d. A current flows in the mainpattern section MPm when the electromagnetic waves that are generatedalong the signal transmission path on the main pattern section MPm ofthe conductor pattern MP1 then arrive. If the frequency band of thesignal transmission path or in other words the frequency band utilizedby the signal transmission path is high-frequency waves, the skin effectcauses a high conduction resistance in the main pattern section MPm. Theelectrical energy is therefore converted into heat energy and at least aportion of the electromagnetic wave is eliminated. In other words, theconductor pattern MP1 functions as an electromagnetic wave absorber thateliminates at least a portion of the electromagnetic wave by Jouleconversion.

In another aspect separate from the main pattern section MPm shown inFIG. 7, when a current flows due to electromagnetic waves, a portion ofthe electromagnetic wave can be eliminated even for example by aconductor pattern shaped as a plane circle not shown in the drawingrather than plural aperture sections MPh formed in a mesh shape.However, the surface area of the main pattern section MPm is preferablylarge from the standpoint of improving efficiency when convertingelectromagnetic wave energy into heat energy. The main pattern sectionMPm of the conductor pattern MP1 of the present embodiment is thereforepreferably a mesh pattern having plural aperture sections MPh atsystematic intervals.

If only considering the function as an electromagnetic wave absorberthen just as with the conductor pattern MP1, there is no need to couplethe conductor plane 2PL and the main pattern section MPm. However, inthis aspect just as is described later on, a portion of theelectromagnetic wave absorber can be utilized as the return path for thesignal transmission path. The conductor plane 2PL and the main patternsection MPm are therefore electrically coupled by way of a couplingsection MPj. Also if the conductor plane 2PL and the main patternsection MPm are electrically coupled, the voltage potential of theconductor pattern MP1 serving as the electromagnetic wave absorber, isstabilized to the same electric potential (for example, groundpotential) as the conductor plane 2PL electric potential.

The electromagnetic wave absorber here is formed with the objective ofsuppressing the scattering of electromagnetic waves along the signaltransmission path and so is formed at a position overlapped with thesection of the wire 2 d forming the signal transmission path in thethickness direction as shown in FIG. 8. The conductor plane 2PL is aground plane supplied with a standard electric potential (for exampleground potential) as already described, and is one section of the returnpath corresponding to the signal transmission path. The electromagneticwave absorber is formed within the aperture section PLh of the conductorplane 2PL as shown in FIG. 7 so that if the conductor plane 2PL is notelectrically coupled to the electromagnetic wave absorber, the returnpath corresponding to the signal transmission path can bypass theperiphery of the aperture section PLh. In other words, the gap distancebetween the signal transmission path and the return path becomes widerin some sections.

Reducing and also setting a fixed gap distance between the signaltransmission path and the return path is preferable from the standpointof reducing crosstalk noise among the plural signal transmission paths.However, when the return path detours along the periphery of theaperture section PLH formed over the conductor plain 2PL as describedabove, then the gap distance between the signal transmission path andreturn path becomes large in certain sections. Consequently, effectsfrom crosstalk noise are easily prone to occur at points where the gapdistance is large. Restated, crosstalk noise immunity decreases incertain sections if the electromagnetic wave absorber and conductorplane 2PL are not coupled each other. Whereupon, the present inventorsmade a further investigation of technology for utilizing a portion ofthe electromagnetic wave absorber as the return path and discovered thestructure of the present embodiment.

In the present embodiment as shown in FIG. 7 and FIG. 8, the conductorpattern MP1 serving as the electromagnetic wave absorber is electricallycoupled to the conductor plane 2PL serving as the ground plane that isthe return path corresponding to the signal transmission path. A portionof the conductor pattern MP1 serving as the electromagnetic waveabsorber can in this way be utilized as the return path corresponding tothe signal transmission path.

The main pattern section MPm for the conductor pattern MP1 as shown inFIG. 7 is formed in a mesh pattern where the plural aperture sectionsMPh are periodically positioned. Each of the aperture sections MPh arethrough holes penetrating through the metal film configuring theconductor pattern MP1 in the thickness direction. In the example shownin FIG. 7 the through holes are arrayed in a grid shape. Making a meshpattern over the planar shape of the main pattern section MPm in thisway forms the return path along the mesh pattern. A return path cantherefore be formed along the direction that the wire 2 d extendsregardless of the layout of the wire 2 d that is formed at a positionoverlapped with the conductor pattern MP1 in the thickness direction.

Also in the present embodiment, plural coupling sections MPj are formedthat link the conductor plane 2PL with the main pattern section MPm.Therefore, a wire 2 d can be formed along the coupling section MPj, ifany or any one of the plural coupling sections MPj is formed in thevicinity of the wire 2 d as seen from a plan view. In the example shownin FIG. 7, one among the plural coupling sections MPj of the conductorpattern MP1 is overlapping the wire 2 d in the thickness direction asseen from a plan view. In this plan view, the coupling section MPj thatis placed nearest the wire 2 d then forms a return path corresponding tothe signal transmission path. In the example shown in FIG. 7, one amongthe plural coupling sections MPj is overlapping the wire 2 d so thatthis coupling section MPj forms a return path.

The present embodiment is in other words capable of suppressingelectromagnetic wave scattering in sections where impedancediscontinuities are observed by way of an electromagnetic wave absorberand also capable of preventing the signal transmission path and returnpath from separating away from each other at certain points by utilizinga portion of the electromagnetic wave absorber as the return path. Also,if the electromagnetic wave absorber can be utilized as the return path,there are no restrictions on the wiring layout for forming theelectromagnetic wave absorber so that many electromagnetic waveabsorbers can be formed in the wiring substrate 2. The noise immunity ofthe semiconductor device 1 shown in FIG. 4 can consequently be improved.

The following can be considered from the standpoint of improving thedegree of freedom in wiring layout design in the present embodiment.Namely, in the present embodiment, a conductor pattern MP1 containing amain pattern section MPm serving as the mesh pattern in a planar shapeis placed at a position overlapped with a portion of the wire 2 d in thethickness direction, and moreover is electrically coupled to theconductor plane 2PL. Therefore, a return path can therefore be formedalong the direction that the wire 2 d extends regardless of the layoutof the wire 2 d so that the degree of freedom in designing (or layingout) the wire 2 d can be improved.

The expression, forming a return path along the direction that the wire2 d (namely the signal transmission path) extends also includes the casewhere the wire 2 d and the overall return path overlap in the thicknessdirection at a position overlapped with the aperture section PLh andalso includes the following cases.

In the examples shown in FIG. 7 and FIG. 8, the planar shape of the wire2 d within the aperture section PLh and the mesh pattern (grid pattern)of the main pattern section MPm of the conductor pattern MP1 are not acomplete match, and there is a section where the aperture sections MPhand the wire 2 d overlap. Restated in other words, there is a sectionwhere the position of the wire 2 d and the position of the conductorpattern MP1 forming the return path deviate as seen from a plan view.

However, the main pattern section MPm is a mesh pattern so the returnpath is formed along the mesh pattern. Therefore, if the diameters ofthe respective aperture sections MPh in the mesh pattern could be madesmaller, the amount of deviation between the return path and wire 2 dcould be reduced. An evaluation by the present inventors, that theamount of deviation (or offset) between the return path and the wire 2 d(signal transmission path) is dependent on the return losscharacteristics that is requested but is preferably 50 μm or lower.

The planar shape of the aperture section MPh shown in the example inFIG. 7 is a quadrangle; and the length of one side of the aperturesection MPh is for example a square of approximately 30 μm to 200 μm.There are various modifications in the size and planar shape of theaperture section MPh. The shape of the aperture section MPh for examplemay be a circle, a square, or even a polygon. The planar shape of theaperture section MPh may be a shape other than a regular polygon orregular (perfect) circle (for example, an oval or rectangular shape,etc.). However, the size of the aperture must be reduced as theoperating frequency becomes higher.

One among the plural coupling sections MPj over the conductor patternMP1 as seen from a plan view in the example shown in FIG. 7 isoverlapping the wire 2 d in the thickness direction. However, asdescribed above, even if there is a deviation between the position ofthe wire 2 d and the position of the conductor pattern MP1 (for example,coupling section MDj) serving as the return path as seen from a planview, the crosstalk noise can be reduced if the amount of deviation (oroffset) is small.

In the present embodiment, the amount of deviation between the couplingsection MPj and the wire 2 d can be reduced even if using an optionalwire 2 d layout design, so that plural coupling sections MPj arepositioned at approximately the same gap distance from each other. Inthe example shown in FIG. 7, the plural coupling sections MPj containtwo coupling sections MPjx that are positioned so as to enclose the mainpattern section MPm, along the virtual line VLx passing through thecenter of the aperture section PLh along the X direction. Also theplural coupling sections MPj contain two coupling sections MPjy that arepositioned so as to enclose the main pattern section MPm, along thevirtual line VLy passing through the center of the aperture section PLhalong the Y direction that intersects the x direction. Also, among thetwo coupling sections MPjx and the two coupling sections MPjy, twocoupling sections MPjs are placed between the respective adjacentcoupling sections MPjx and coupling section MPjy. Each coupling sectionMPj is placed so as to align the mutual gap distances (so as to beapproximately the same).

The number of coupling sections MPjs placed between the coupling sectionMPjx and the coupling section MPjy can be applied to a variety ofmodifications according to the size of the aperture section PLh. If forexample the aperture area of the aperture section PLh is sufficientlysmall, the coupling section MPjs need not be placed if the offset ordeviation amount is within the tolerance range wherever the wire 2 d ispositioned between the coupling section MPjx and the coupling sectionMPjy. Also for example if one coupling section MPjs is positionedbetween the coupling section MPjx and the coupling section MPjy, onecoupling section MPjs may be placed in the case that the deviation oroffset amount of the wire 2 d is within the tolerance range. Moreover,if the aperture area of the aperture section PLh is large, three or morecoupling sections MPjs may be placed between the coupling section MPjxand the coupling section MPjy. However, from the standpoint of improvingthe degree of freedom for the wire 2 d layout design, the planar shapeof the conductor pattern MP1 is preferably point symmetric with thecenter of the aperture section PLh even if a number of coupling sectionsMPjs are placed.

As shown in FIG. 7, each of the plural coupling sections MPjs extends ata 45 degree slope in the X direction and the Y direction. By arrangingthe direction that the coupling section MPjs extends at a 45 degreeslope in the X direction and Y direction, the gap distance between theplural coupling sections MPjs can be easily aligned. Also in designingthe wire layout, the wire is in many cases laid out with the two axesserving as the reference (for example X axis and Y axis) and a thirdaxis with a 45 degree slope in combination with the two axes serving asthe reference. The wire 2 d that forms the signal transmission path suchas shown in FIG. 7 for example, contains plural bends, and the bendangles are multiple of 45 degrees (angles in section less than 180degrees are any among 45 degrees, 90 degrees, or 135 degrees).Therefore, the directions that the wire 2 d extends and the directionthat the coupling section MPjs extends are easy to align, when thedirection that the coupling section MPjs extends is at a 45 degree sloperelative to the X direction and the Y direction as shown in FIG. 7.

<Position for Placing the Electromagnetic Wave Absorber>

The position for placing the conductor pattern MP1 serving as theelectromagnetic wave absorber described in FIG. 7 and FIG. 8 isdescribed next. FIG. 9 is an enlarged cross-sectional view for aposition different from FIG. 8. FIG. 10 is an enlarged cross-sectionalview showing the essential structure of the conductor pattern for theenlarged cross-sectional view in FIG. 9. FIG. 11 is an enlargedcross-sectional view showing the modification corresponding to FIG. 9.

In FIG. 9 and FIG. 11, the section where the main pattern section MPm ofthe conductor pattern MP1 is shown by applying hatching, and the pluralaperture sections formed over the conductor pattern MP1 are not shown inthe drawings. Also in FIG. 9 and FIG. 11, the coupling section MPj isshown by a dotted line in order to diagrammatically show that the mainpattern section MPm of the conductor pattern MP1 and the conductor plane2PL are electrically coupled. The conductor plane 2PL coupled to theconductor plane MP1 is omitted from the drawing to make the drawingeasier to understand visually.

The conductor plane serving as the electromagnetic wave absorber isformed in sections where the wiring structure changes as alreadydescribed. In the example in FIG. 8, the conductor pattern MP1 is formedat a position overlapped with the land 2LD in the thickness direction.

In the example shown in FIG. 8, the wiring substrate 2 includes thewiring layer WL1 where the wire 2 d serving as the signal transmissionpath, the wiring layer WL2 that is adjacent to the upper layer side(chip mounting surface side) of the wiring layer WL1 and the conductorpattern MP1 is formed, and the wiring layer WL3 that is adjacent to thelower layer side (mounting surface side) of the wiring layer WL1 and thesignal transmission path is formed. The wire 2 d and the land 2LD areelectrically coupled by way of the via wires 2V serving as the interlayer conduction path. The land 2LD is an external terminal of thesemiconductor device 1 (See FIG. 4) and is coupled to the solder ball(See FIG. 4) so that the width of the land must be prepared so as to besufficiently larger than the wire 2 d.

In FIG. 8, when signals are sent to the wire 2 d (signal current isflowing), and the frequency of the signal is sufficiently high, a largesignal reflection occurs at the coupling section for the via wire 2Vthat electrically couples the land 2LD and the wire 2 d so that ascattered electromagnetic wave occurs. Signal reflection tends to easilyoccur in sections that electrically couple the wire 2 d that is formedinto a narrow wire shape, and land 2LD that is a metal pattern whosewidth is sufficiently larger than the wire 2 d, rather than in sectionscoupling the wires 2 d together. When these scattered electromagneticwaves widen outwards, the transmission performance along the signaltransmission path deteriorates. Whereupon in the present embodiment, aconductor pattern MP1 is formed at a position overlapped with the land2LD in the thickness direction, and a wire 2 d to transfer signals(signal current flows) is placed between the conductor pattern MP1 andthe land 2LD. Moreover, in the example shown in FIG. 6, the via wire 2Vis formed between the land 2LD and the conductor pattern MP1 (in otherwords, at a position overlapped with the land 2LD and the conductorpattern MP1 in the thickness direction).

In this way, at least a portion of the scattered electromagnetic wavesemitted in the sections where the wiring structure changes are trappedby the conductor pattern MP1, and eliminated by conversion to heatenergy. From the standpoint of easily trapping scattered electromagneticwaves, the aperture diameter (length of one side, when the planar shapeis a quadrangle) of the aperture section MPh, is preferably smaller thanthe wavelength of the electromagnetic waves corresponding to the signalband of the signal that is sent. Also, the aperture diameter (length ofone side, when the planar shape is a quadrangle) of the aperture sectionMPh is in particular preferably 1/20^(th) or less than the wavelength ofthe above described electromagnetic waves.

Also in the present embodiment, in the wiring layer WL2 the conductorplane MP1 and the conductor plane 2PL are electrically coupled by way ofthe plural coupling sections MPj (See FIG. 7) so that the gap distancebetween the signal transmission path and the return path gap can bemaintained at a fixed distance. Therefore, crosstalk noise occurring dueto the distance in local sections between the signal transmission pathand the return path can in this way be prevented.

In the examples shown in FIG. 7 and FIG. 8, the conductor pattern MP1 isdescribed as formed at a position overlapped with the land 2LD. However,there are other sections having changes in the wire structure. Forexample when the plural insulation layer 2 e in the wiring substrate 2 econtains an insulation layer (core layer, core insulation layer) 2CRmade from prepeg material as shown in FIG. 9, the through hole wire 2TWelectrically coupling the upper surface 2Ca and the lower surface 2Cb ofthe insulation layer 2 e, is coupled to the through hole land 2TL havinga larger width (diameter) than the wire 2 d.

In the example shown in FIG. 9, on the lower surface 2Cb side of theinsulation layer 2CR serving as the core layer; the wiring substrate 2includes the wiring layer WL1 where the wire 2 d serving as the signaltransmission path is formed, the wiring layer WL2 that is adjacent tothe lower side (mounting surface side) of the wire layer WL1 and wherethe conductor pattern MP1 is formed, and a wiring layer WL3 that isadjacent to the upper layer side (chip mounting surface side) of thewiring layer WL1 and where a through hole land 2TL is formed. On theupper surface 2Ca side of the insulation layer 2CR serving as the corelayer, the wiring substrate 2 includes the wiring layer WL4 where thewire 2 d serving as the signal transmission path is formed, the wiringlayer WL5 that is adjacent to the upper layer side (chip mountingsurface side) of the wiring layer WL4 and where the conductor patternMP1 is formed, and a wiring layer WL6 that is adjacent to the lowerlayer side (mounting surface side) of the wiring layer WL4 and where thethrough hole land 2TL is formed.

The through hole land 2TL is for example a planar shape having acircular conductor pattern. The diameter (width) of the through holeland 2TL is a smaller than the diameter of the land 2LD shown in FIG. 8but larger than the width of the wire 2 d. The insulation layer 2CRserving as the core layer is comparatively hard in comparison to theother insulation layers (build-up layers) formed by the build-uptechnique and has a large thickness so the diameter of the through holewire 2TW is larger than the diameter of the via wire 2V formed in thebuilt-up layer. Therefore, the width of the through hole land 2TL formedat both ends of the through hole wire 2TW is larger than the diameter ofthe width of the wire 2 d and the via wire 2V.

In FIG. 9, when signals are sent to the wire 2 d (signal current isflowing), and the frequency of the signal is sufficiently high, signalreflection occurs at the coupling section for the via wire 2V thatelectrically couples the through hole land 2TL and wire 2 d so thatscattered electromagnetic wave occurs. Signal reflection occursrespectively at the upper surface 2Ca side and the lower surface 2Cbside of the insulation layer 2CR serving as the core layer.

Whereupon in the present embodiment, the conductor patterns MP1 arerespectively formed at a position overlapped with the through hole land2TL in the thickness direction, and a wire 2 d to transmit signals(signal current flows) is placed between the conductor pattern MP1 andthe through hole land 2TL. Moreover, in the example shown in FIG. 9, thevia wire 2V is formed between the through hole land 2TL and theconductor pattern MP1 (in other words, at a position overlapped with thethrough hole land 2TL and the conductor pattern MP1 in the thicknessdirection).

In this way, at least a portion of the scattered electromagnetic wavesemitted at the coupling section for the via wire 2V that electricallycouples the through hole land 2TL and wire 2 d is trapped by theconductor pattern MP1, and eliminated by conversion to heat energy. Thepreferred shape of the conductor pattern MP1 is the same as previouslydescribed using FIG. 7 and FIG. 8 so a redundant description is omitted.

In the example shown in FIG. 9 however, a wiring layer WL3 where theconductor pattern MP1 is formed; and a wiring layer WL3 where a land 2LDis formed as shown in FIG. 8 so that in some cases the wiring layer 3cannot be formed due to the position of the land 2LD. In such cases,placement priority is given to the land 2LD (See FIG. 8) and theconductor pattern MP1 is formed at sections not overlapping the land 2LDand the through hold land 2T.

When the through hole land 2TL and the land 2LD overlap the thicknessdirection due to the relation between the layout and quantity of thethrough hole lands 2TL and the lands 2LD, the number of wiring layersmay be increased, and a conductor pattern MP1 can be formed between thethrough hole lands 2TL and the lands 2LD that overlap in the thicknessdirection as in the modifications shown in FIG. 11 and FIG. 12.

The wiring substrate 2A of the modification shown in FIG. 11 differsfrom the wiring substrate 2 shown in FIG. 9 in the point that a wiringlayer WL7 where a land 2LD is formed, is mounted adjacent to the furtherlower layer side (mounting surface side) of the wiring layer WL3 wherethe conductor pattern MP1 is formed. Seen from a different view, thewiring substrate 2A for the modification shown in FIG. 11 differs fromthe wiring substrate 2 shown in FIG. 9 in the point that pluralconductor patterns MP1 are formed over the wiring layer WL3, andmoreover plural lands 2LD are formed over a wiring layer WL7 differentfrom the wiring layer WL3. The wiring substrate 2A also contains awiring layer WL1 where the wire 2 d for transmitting signals (signalcurrent flows) and the wiring layer WL3 where the conductor pattern MP1is formed, and that are formed between the wiring layer WL2 where thethrough hole land 2TL is formed and the wiring layer WL7 where the land2LD is formed.

In the case of the wiring substrate 2A, the number of wiring layersincreases more than the wiring substrate 2 shown in FIG. 8 and FIG. 9.However, even if the land 2LD and the through hole land 2TL overlap inthe thickness direction, the conductive pattern MP1 serving as theelectromagnetic wave absorber can be placed at the position where thethrough hole land 2TL and the land 2LD overlap in the thicknessdirection. Therefore, the widening of the scattered electromagnetic wavethat occurs in the coupling section of the through hole land 2TL and thewire 2 d can be prevented.

The land 2LD shown in FIG. 11 is an external terminal that supplies thestandard (or reference) electric potential. A portion of the conductorplane 2PL is therefore exposed from the insulation layer 2 e and isutilized as the land 2LD. In this case, a via wire 2V coupling theconductor plane 2PL of the wiring layer WL7 and the conductor plane 2PLof the wiring layer WL3 can be placed at a position not overlapping theconductor pattern MP1. A conductor pattern MP1 having the same planarshape as the conductor pattern MP1 shown for example in FIG. 7 cantherefore be formed as an electromagnetic wave absorber.

The wiring substrate 2B for the modification shown in FIG. 12, differsfrom the wiring substrate 2A shown in FIG. 11 in the point that a wiringlayer WL9 is mounted formed with a wire 2 d coupling to the land 2LDbetween the wiring layer WL7 formed with a land 2LD and a wiring layerWL3 formed with a conductor pattern MP1. The wire 2 d formed in thewiring layer WL9 is a portion of the signal transmission path (signalcurrent flows) that transmits the same or different signals as the wire2 d formed in the wiring layer WL1; and is coupled by way of the viawire 2V to the land 2LD. Seen in another way, the wiring substrate 2Bfor the modification shown in FIG. 12 differs from the wiring substrate2A shown in FIG. 11 in the point that the wire 2 d that configures therespective signal paths (signal current flows) is formed in the upperlayer and the lower layer of the conductor pattern MP1.

In the case of the wiring substrate 2B, the number of wires is increasedeven more than the wiring substrate 2A shown in FIG. 11. However, aconductor pattern MP1 serving as an electromagnetic wave absorber can beplaced at a position overlapped with the wire 2 d coupled to the throughhole land 2TL and the wire 2 d coupled to the land 2LD in the thicknessdirection, even if the land 2LD that is a signal transmission path, andthe through hole land 2TL that is a signal transmission path overlap inthe thickness direction. The widening of the scattered electromagneticwaves emitted in the section coupling the wire 2 d and the through holeland 2TL towards the land 2LD can therefore be prevented. Moreover, thewidening of the scattered electromagnetic wave emitted in the sectioncoupling the land 2LD and the wire 2 d towards the though hole land 2TLcan be prevented. In other words, in the case of the wiring substrate2B, the effect of the electromagnetic waves that are emitted at thelower layer of the conductor pattern MP1 and the electromagnetic wavesgenerated in the upper layer of the conductor pattern MP1 can berespectively decreased by the conductor pattern MP1 formed in the wiringlayer WL3.

Also, in the case of the wiring substrate 2B, the signal current flowingin the wire 2 d that is formed in the wiring layer WL9, and the signalcurrent flowing in the wire 2 d that is formed in the wiring layer WL1may be the same signal current or may be a different signal current. Inother words, the effect can also be achieved for the case where the wire2 d formed in the wiring layer WL9 and the wire 2 d formed in the wiringlayer WL1 configure one signal transmission path, or the case whereconfiguring another signal transmission path.

The wiring substrate 2A shown in FIG. 11 contains a wiring layer WL8formed with a conductor plane 2PL formed in a further upper layer of thewiring layer WL5 where a conductor pattern MP1 is formed. The wiringsubstrate 2B shown in FIG. 12 contains a wiring layer WL10 where aconductor plane 2PL is formed between the wiring layer WL8 and thewiring layer WL. The wiring layer WL8 that is shown in FIG. 11 and FIG.12 or the wiring layer WL10 that is shown in FIG. 12 can be omitted whenthere is no large diameter (width) pattern such as the land 2LD that isformed on the upper surface 2Ca side of the insulation layer 2CR.However, from the standpoint of suppressing curvature deformation on thewiring substrate by approaching the values for the expansioncoefficients on the upper surface 2Ca side and lower surface 2Cb side ofthe insulation layer 2CR serving as the core layer, the number of layersin the wiring layers that are formed on the upper surface 2Ca side andlower surface 2Cb side of the insulation layer 2CR are preferably thesame.

When many conductor patterns MP1 are formed over a single wiring layerof the wiring substrate 2, plural signal transmission paths mightoverlap over one conductor pattern MP1. For example, in the examplesshown in FIG. 13 and FIG. 14, a wire 2 d 1 is formed to transmit a firstsignal to a wiring layer of a lower layer adjacent to the wiring layerwhere the conductor pattern MP1 is formed. Also, a wire 2 d 2 is formedto transmit a second signal different from the first signal current, tothe wiring layer of an upper layer adjacent to the wiring layer wherethe conductor pattern MP1 is formed. Respectively different types ofsignals are transmitted to the wire 2 d 1 and the wire 2 d 2 so thatcrosstalk noise is emitted when the return paths of each signaltransmission path overlap.

However the conductor pattern MP1 of the present embodiment iselectrically coupled by way of plural couplings MPj to a conductor plane2PL (See FIG. 13) serving as the ground plane as already described. Aportion of the of the conductor pattern MP1 can therefore be utilized asthe return path so that overlapping the return path for each signaltransmission path becomes difficult. Also in the present embodiment, thedistances for the return path and the signal transmission path can madenearly as described above. Therefore the effect from crosstalk noise inthe signal paths can be reduced.

<Manufacturing Method for Semiconductor Device>

The manufacturing method (assembly method) for the for the semiconductordevice 1 shown in FIG. 1 through FIG. 4 shown in FIG. 1 through FIG. 4is described next while referring to the flow chart shown in FIG. 15.FIG. 15 is a drawing for describing the flow in the assembly process forthe semiconductor device shown in FIG. 1 through FIG. 4. In thefollowing description for the manufacturing method, a wiring substrate 2formed in advance for the product size is prepared and the method formanufacturing a single semiconductor device 1 is described. However as amodification, a so-called multi-piece board segmented into pluralproduct forming regions is prepared, and after assembly for therespective product forming regions, the multi-piece manufacturing methodcan also be applied to sub-divide into each of the product formingregions and obtain plural semiconductor devices. The unit piecemanufacturing process that is applied during the multi-piecemanufacturing method is therefore written in parentheses in FIG. 15.

In the substrate preparation process shown in FIG. 15, the wiringsubstrate 2 shown in FIG. 4 is first of all prepared. Besidespreparation for manufacturing the wiring substrate 2, the expression“preparing the wiring substrate 2” also includes the purchase of afinished product wiring substrate 2 and performing preparation. Exceptfor the point that solder ball 4 shown in FIG. 4 is still not coupled,and the point that the semiconductor chip 3 is not mounted, the wiringsubstrate 2 prepared in this process is a structural material that ispre-formed as described while referring to FIG. 1 through FIG. 14.However, solder material (solder bumps) are each pre-formed joined tothe projecting electrodes 3BP, over the plural bonding pads 2PD of thewiring substrate 2.

The semiconductor pattern MP1 shown in FIG. 7 through FIG. 14 is forexample formed as described below. FIG. 16 is a drawing fordiagrammatically describing the production process for forming theconductor pattern serving as the electromagnetic wave absorber over thewiring substrate in the substrate preparation process shown in FIG. 15.

The semiconductor pattern MP1 shown in FIG. 7 through FIG. 14 iscollectively formed simultaneous with the other metal patterns formed inthe same layer (same wiring layer) such as the conductor plane 2PL andthe wire 2 d shown in FIG. 4. In the example shown in FIG. 16, a maskMSK in a film shape is first of all formed over the conductor patternsurface of the insulation layer 2 e as the mask forming process. Themask MSK is formed in a position where the conductor pattern MP1 (SeeFIG. 7) is not formed, and in the example shown in FIG. 7, the mask MSKis formed in a section corresponding to the plural aperture sections MPhor the aperture section PLh.

Next, a metal film that is formed by metal deposition patterning isdeposited in the aperture section of the mask MSK as forming theconductor pattern. This metal film is comprised of the conductor patternMP1 and the conductor plane 2PL.

Next, in the mask stripping process, the film shaped mask MSK isremoved. When the mask MSK is removed, the aperture MPh and aperture PLhare formed over the section where the mask MSK is present.

Next, in the insulation layer forming process, an insulation layer 2 eserving as the built-up layer is formed so as to cover the conductorpattern MP1 and the conductor plane 2PL. In this process, an insulationlayer 2 e is embedded within the aperture section MPh and within theaperture section PLh of the conductor pattern MP1.

The above described conductor pattern MP1 of the present embodiment isformed at one time simultaneous with the conductor plane 2PL or wire 2 d(See FIG. 4) so that there are no further manufacturing processadditions even if a conductor pattern MP1 is formed.

In the semiconductor chip preparation process shown in FIG. 15, thesemiconductor chip 3 shown in FIG. 4 is prepared. An insulation film isformed over the surface 3 a of the semiconductor chip 3 so as to coverthe base material and wiring of the semiconductor chip 3. The respectivesurfaces of the plural pads 3PD are exposed from the insulation film atthe aperture section formed over this insulation film. The plural pads3PD are each comprised of a metal and in the present embodiment are forexample aluminum (Al). Plural projecting electrodes 3BP are respectivelycoupled to the plural pads 3PD, and the plural pads 3PD of semiconductorchip 3 and the plural bonding pads 2PD of the wiring substrate 2 arerespectively electrically coupled by way of the plural projectingelectrodes 3BP. The projecting electrodes 3BP are for example stackedsolder material or a so-called solder bump stacked by way of anunderlayer metal film (under-bump metal) over the pad 3PD.

Next, in the semiconductor chip mounting process, a semiconductor chip 3such as shown in FIG. 4 is mounted over the upper surface 2 a serving asthe chip mounting surface of the wiring substrate 2. In the presentembodiment, mounting is performed by the face down mounting method (orthe flip chip method) so that the surface 3 a where the plural pads 3PDare formed is facing opposite the upper surface 2 a of the wiringsubstrate 2. In this case, the circuits formed over the semiconductorchip 3, and the circuits (transmission circuit) formed over the wiringsubstrate 2 are electrically coupled by joining the solder bumpsrespectively formed over the plural bonding pads 2PD of the wiringsubstrate with the plural projecting electrodes 3BP.

Next, in the underfill filling process, the underfill resin (insulationfilm resin) 5 is placed between the semiconductor chip 3 and wiringsubstrate 2 as shown in FIG. 4. The underfill resin 5 is placed so as toseal the space between the surface 3 a of the semiconductor chip 3 andthe upper surface 2 a of the wiring substrate 2. The underfill resin 5is comprised of insulation material (non-conducting material) (forexample resin material) and is filled so as to seal the electricalcoupling section (coupling section for the plural projecting electrodes3BP) of the semiconductor chip 3 and the wiring substrate 2.

Another mounting method as a modification utilizing the underfill resin5 can be applied in which prior to the semiconductor chip mountingprocess shown in FIG. 15, a pre-coating of resin material as a film or apaste (not shown in drawing) can be applied over the chip mountingregion serving as the scheduled region for mounting the semiconductorchip 3, and the semiconductor chip 3 pressed from over the insulationmaterial.

Next, in the ball mount process, plural solder balls 4 are mounted onthe lower surface 2 b side serving as the mounting surface for thewiring substrate 2. In this process, the plural solder balls 4 areplaced over the land 2LD exposed from the insulation layer 2 e on themounting surface side shown in FIG. 4, and the plural solder balls 4 canbe mounted by reflow processing (process for cooling after heating thesolder components and melt-joining).

When performing the unit piece manufacturing process, in order to obtainthe plural semiconductor devices 1, the unit pieces are made in eachproduct forming region by slicing the wiring substrate used for themulti-piece manufacturing along the dicing line (parting line) thatsegments the plural product forming regions.

Afterwards, the necessary testing and inspections such as for externalinspections and electrical tests are performed, and shipping or boardmounting not shown in the drawings is performed.

<Modifications>

The specific description given above is based on the embodiment of theinvention rendered by the present inventors. However the presentinvention is not limited to the embodiment and needless to say, allmanner of modifications not departing from the spirit and scope of thepresent invention are permissible. A number of modifications of theembodiment are already described but representative modifications of theabove described embodiment are hereafter described.

In the above described embodiment, an example of the semiconductordevice 1 is described as shown in FIG. 4 utilizing a wiring substrate 2containing an insulation layer 2CR comprised of prepreg material as thecore layer. However, the technology described for the embodiment mayalso apply to a so-called coreless substrate formed by stacking build-uplayers not containing a core. In this case, no through hole wire 2TW andno through hole land 2TL penetrating through the core layer are formed.Therefore, the noise immunity of the semiconductor device 1 can beimproved if the conductor pattern MP1 is formed at a position mainlyoverlapped with the land 2LD in the thickness direction as shown in FIG.8.

Also, as signal types in the above embodiment, an example is describedutilizing so-called single-end signals where the “H” level and “L” levelare set as the signal voltage levels with ground electric potential asthe standard. However, among the signal types there are differentialsignals in which signals electric potentials are respectively suppliedto a pair of signal transmission paths (differential pair) and theelectric potential difference for the differential pair are set to the“H” level and “L” level. The technology described for the aboveembodiment can also be applied to signal transmission paths fortransmitting differential signals. FIG. 17 is an enlarged plan viewshowing modification corresponding to FIG. 7.

The wiring substrate 2D shown in FIG. 17 differs from the wiringsubstrate 2 shown in FIG. 7 in the point that a differential signalflows in the wire 2 d. More specifically, an aperture section PLh isformed at a position overlapped with a portion of the wire 2 d 3 that isone of the differential pair in the thickness direction, in theconductor plane 2PL of the wiring layer where the conductor plane MP1 isformed among the wiring layers of the wiring substrate 2D. Moreover,another aperture section PLh is formed at a position overlapped with aportion of the wire 2 d 4 that is the other portion of the differentialpair in the thickness direction, in the conductor plane 2PL. Also,respective conductor patterns MP1 are formed in the two differentaperture sections PLh.

The differential pair is comprised of the wire 2 d 3 and the wire 2 d 4,and these configure the signal transmission path along which thedifferential signals are sent. The wire 2 d 3 and the wire 2 d 4 aremutually formed in the same wiring layer, and the wiring layer where theconductor pattern MP1 is formed is adjacent to the wiring layer wherethe wire 2 d 3 and the wire 2 d 4 are formed.

In the case of the single-end signal that is described in the aboveembodiment, maintaining a fixed gap distance for the signal transmissionpath and the return path is described as an essential noisecountermeasure. In the case of the differential signal, besidesmaintaining each signal transmission path and return path at a fixed gapdistance, matching the impedance along the signal transmission path pairis also important. In the modification shown in FIG. 17, electricallycoupling each of the conductor patterns MP1 to the conductor plane 2PLserving as the ground plane, allows the conductor pattern MP1 serving asthe electromagnetic wave absorber to function as a portion of the returnpath for each signal transmission path.

The main pattern section MPm of the conductor pattern MP1, is comprisedof mesh patterns containing plural aperture sections MPh placed atregular intervals. Utilizing a mesh pattern for the planar shape of themain pattern section MPm results in a return path that is formed alongthe mesh shape. Therefore, a return path can be formed along thedirection that the wires 2 d 3, 2 d 4 extend, regardless of the layoutof the wires 2 d 3, 2 d 4 that are formed at positions overlapped withthe conductor pattern MP1 in the thickness direction.

Therefore, impedance matching of the differential pair can be easilyattained in the wiring substrate 2D shown in FIG. 17 if the shapes ofthe wire 2 d 3 and the wire 2 d 4 serving as the differential pair canbe configured in appropriate shapes. Also, in the above describedembodiment, forming plural coupling sections MPj to couple the conductorplane 2PL with the main pattern section MPm allows forming the wires 2 d3, 2 d 4 along the coupling section MPj.

Though a redundant description is omitted, the preferred shape of theconductor pattern MP1 (for example a shape preferred from the standpointof improving the degree of freedom of the wiring layout) of the abovedescribed embodiment, can be applied in the same way to an embodimentfor transmitting the differential signal shown in FIG. 17. In this case,using the same shape for the conductor pattern MP1 overlapping the wire2 d 4 and the conductor pattern MP1 overlapping the wire 2 d 3 ispreferable from the standpoint achieving impedance matching.

In the above embodiment, an example of a plural square aperture sectionsMPh arrayed a grid shape is described as an example of the planar shapeof the main pattern section MPm of the conductor pattern MP1, howevervarious modifications can be applied. In the wiring substrate 2E shownin FIG. 18 for example, the aperture shapes of the plural aperturesections MPh formed in the main pattern section (mesh pattern section)MPm of the conductor pattern MP1, form a circle. Also for example, inthe wiring substrate 2F shown in FIG. 19, the aperture shapes of theplural aperture sections MPh formed in the main pattern section (meshpattern section) MPm of the conductor pattern MP1, form a rectangle.

As described by utilizing shown in FIG. 16, when utilizing the mask MSKduring the forming of the conductor pattern MP1 serving as the meshpattern, peeling of the mask MSK might occur during the manufacturingprocess when the aperture diameter of the aperture section MPh becomessmall. As shown for the wiring substrate 2F shown in FIG. 19, the planararea of the mask MSK becomes large if the aperture shape of the aperturesection MPh is a rectangle so the peeling of the mask MSK prior to theprocess for forming the conductor pattern shown in FIG. 16 can beprevented.

In the wiring substrate 2G shown in FIG. 20, the shape of the pluralaperture sections MPh formed in the main pattern section (mesh patternsection) MPm of the conductor pattern MP1 is a mix of squares andrectangle shapes. Also, in the plural aperture sections MPh of thewiring substrate 2F, among the long side LS and short side SS formingthe contour of the plural rectangle, the short side SS are arrayed in azigzag shape so as not to form a single row relative to the Y direction.In this case, the extent of the offset or deviation between the returnpath and the wire 2 d can be suppressed even when the planar area of theaperture section MPh becomes large. In FIG. 20, an example is shown ofmixing the rectangular aperture sections MPh and the square aperturesections MPh in order to achieve a zigzag array however the array can beachieved just by using the rectangular aperture sections MPh.

When the aperture section MPh is a mix of rectangular aperture sectionsMPh and square aperture section MPh as in the wiring substrate 2G shownin FIG. 20, forming the planar shape of the conductor pattern MP1 so asto be point-symmetric relative to the center of the aperture section PLhis difficult as in the wiring substrate 2 shown in FIG. 16. In thiscase, from the standpoint of improving the degree of freedom in thelayout design of the wire 2 d, the planar shape of the conductor patternMP1 is preferably line-symmetric with one (for example, the virtual lineVLy in the example shown in FIG. 20) of the center lines passing throughthe center of the aperture section PLh, even in the case where somenumber of coupling sections MPjs are placed.

The various above described modifications can also be effectivelyapplied as combinations of each of the above described embodiments.

Extracting the representative technical concept for the semiconductordevice and the semiconductor device manufacturing method of the abovedescribed embodiment and modifications allows stating the followingaspects.

Supplementary Note 1

A manufacturing method for a semiconductor device including:

(a) a process that prepares a wiring substrate comprised of a chipmounting surface, a mounting surface placed on the side opposite thechip mounting surface, plural first terminals placed over a chipmounting surface, plural second terminal placed on the mounting surface,and plural layers of wiring layers electrically coupling the pluralfirst terminals and the plural second terminals;

(b) a process that mounts a semiconductor chip including a surface whereplural electrode pads are formed, and a rear surface that is placed onthe opposite side of the surface, over a semiconductor chip mountingsurface of a wiring substrate and the plural electrode pads of thesemiconductor chip and the plural first terminals are respectivelyelectrically coupled;

the plural wiring layers include a first wiring layer in which a firstwiring layer is formed where a first signal is transmitted, and a secondwiring layer mounted adjacent to the upper layer and the lower layer ofthe first wiring layer,

-   -   a first conductor plate containing a first aperture section at a        position overlapped with a portion of the first wire in the        thickness direction, and a first conductor pattern placed within        the first aperture section of the first conductor plate are        formed over the second wiring layer,    -   the first aperture section is formed so as to pass through the        first conductor place in the thickness direction, and    -   the first conductor pattern includes a mesh pattern section that        is isolated from the first conductor plate, and plural coupling        sections that couple the mesh pattern section and the first        conductor plate.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor chip including a obverse surface, a rear surface oppositethe obverse surface, and an electrode pad formed on the obverse surface;a wiring substrate including a first main surface, a second main surfaceopposite the first main surface, a terminal formed on the first mainsurface and electrically connected with the electrode pad of thesemiconductor chip which is mounted on the wiring substrate such thatthe obverse surface faces the first main surface of the wiringsubstrate; wiring layers including a first wiring layer and a secondwiring layer; a first wire formed in the first wiring layer, the secondwiring layer formed between the first main surface and the first wiringlayer in a thickness direction; a first plate formed in the secondwiring layer and having a first aperture section at a positionoverlapped with a portion of the first wire; and a first pattern formedwithin the first aperture section in the second wiring layer and havinga plurality of openings, wherein the first pattern is electrically andmechanically connected with the first plate by way of a plurality offirst coupling sections in the second wiring layer, and wherein aninterval between two openings next to each other of the plurality of theopenings is greater than or equal to a width of each of the plurality offirst coupling sections in a plan view.
 2. The semiconductor deviceaccording to claim 1, wherein the first pattern includes a mesh patternsection in the plan view.
 3. The semiconductor device according to claim1, wherein the wiring substrate includes: a core layer that includes afirst surface positioned on the first main surface side of the wiringsubstrate, and a second surface opposite the first surface; a throughhole electrode that passes through from the first surface of the corelayer to the second surface of the core layer in the thicknessdirection; and a first through hole land that is connected with thethrough hole electrode on the first surface and that is connected withthe first wire by way of a first via wire in the thickness direction,and wherein the first pattern is formed above the first through holeland and overlaps the first through hole land.
 4. The semiconductordevice according to claim 3, wherein the wiring substrate includes: asecond through hole land that is connected with the through holeelectrode on the second surface in the thickness direction; and a secondpattern that is formed below the second through hole land in thethickness direction, and wherein the second pattern overlaps the secondthrough hole land.
 5. The semiconductor device according to claim 4,wherein the first pattern and the second pattern are the same shape. 6.The semiconductor device according to claim 5, wherein a length of thesecond pattern is larger than a length of the first pattern in adirection along the first main surface of the wiring substrate.
 7. Thesemiconductor device according to claim 5, wherein the second patternincludes a plurality of openings.
 8. The semiconductor device accordingto claim 5, wherein the second pattern includes a mesh pattern sectionin the plan view.
 9. The semiconductor device according to claim 5,wherein the wiring substrate includes a second wire that is formedbetween the second through hole land and the second pattern, and whereinthe second wire is connected with the second through hole land by way ofa second via wire in the thickness direction.
 10. The semiconductordevice according to claim 5, wherein the wiring substrate includes: athird wiring layer that is formed between the second pattern and thesecond main surface of the wiring substrate; and a second plate that isformed in the third wiring layer and has a second aperture section at aposition overlapped with a portion of the second wire, wherein thesecond pattern is arranged in the second aperture section of the secondplate, and wherein the second pattern is connected with the second plateby way of a plurality of second coupling sections.
 11. The semiconductordevice according to claim 1, further comprising an external electrodeformed on the second main surface and electrically connected with theterminal via a plurality of wiring layers.